Running the Visit Planner with APT for JWST


The Visit Planner (click here to see the movie) is the tool that allows for the determination of the schedulability of the Observations (visits). Prior to submission, the Visit Planner will need to have been run on the entire proposal.

Before initiating the Visit Planner, select the Observation or Observations you wish to process; selecting the "Observations" container will process all Observations in the proposal. Note that, to properly determine the schedulability of a Observation, all Observations that are linked to that Observation (e.g. with a GROUP WITHIN) should be processed at the same time. Therefore, selecting one Observation from a linked set will result in ALL linked Observationss being processed.

When the Visit Planner is initialized, all selected Observations appear with a , which indicates that the display is out of date with what is in the proposal. If the Observation has never been processed, the display states that schedulability of the Observation has not yet been computed.

Processing the Observation(s)

To process the Observation, hit the Update Display button. There is a progress wheel to indicate the tool is processing, and the results are cached across sessions.When complete, the total Observation schedulability is displayed. The Update Display button is now inactive - this indicates that the display is now up-to-date. To examine the details of the constraints, open the key on the left of each Observation and then a Visit. There are 2 types of constraints - Relative Constraints are ones that link visits together (e.g. AFTER OBSERVATION BY), while Absolute Constraints are those that are set for an individual visit (e.g. V3PA, Guide Star Constraints).

Each Observation/Visit is labeled in the display, and placing your cursor on the label brings up a tool-tip giving the status (schedulable or unschedulable) of the Observation/Visit; placing your cursor in the timeline brings up a tool-tip which gives more details (schedulable or unschedulable, and the time range). You can also bring up a ruler by clicking anywhere in the display area. You can then drag the ruler to where you want (or just click in the display at the position of interest), and the box will display the Year/Day Number/Time of the ruler location. There are also reports available to indicate which V3PA (orientations) are available, as well as when Guide Stars are available. For more on specifying position angles for JWST, see Assigning Position Angles for JWST Observations.

A indicates the Observation/Visit is schedulable, while an unschedulable visit is indicated by a (and has no total visibility). When examining problems, you should first check the Guide Star constraint, and then the constraints that you specified in the proposal.

We will now do 3 examples on how to resolve unschedulable Observations.


In this example, we have two Observations (3 and 4) that are linked with a 4 AFTER 3 BY 70 TO 75 DAYS. After running the Visit Planner and opening up the Visit, we can see that the AFTER is causing the Observation to be unschedulable. The first Observation is schedulabled from April 5 to June 2, so the second Observation must between June 14 and August 16, which is not schedulable.

So, to make the Observations schedulable, we must revise our AFTER requirement to 80-85 days (to fit in the schedulable window).

Example 2 - V3PA

In this example, we have specified an V3 Position Angle of 70-75 degrees. After running Visit Planner, we see that the V3PA is causing the Observation to be unschedulable.

To see which V3PA values are legal for our target, we first must remove the V3PA requirement and rerun the Observation through the Visit Planner. Now we can bring up the Total Roll Analysis report. The report can be accessed in 2 ways - from the Reports button at the bottom of the display, or by right clicking on the Visit name.

While the Observation can schedule with V3PA from 76-122, we want to select a value close to the one the we originally specified, but one that also allows for some scheduling flexibility (e.g. where the number of available days is at least 10, when possible). In the case, we will choose V3PA = 80-85.

Example 3 - Guide Star/V3PA conflict

In this example, we have specified a V3PA (183-183) for our small mosaic. Looking at the constraints, we see the problem are the Total Absolute and Absolute Roll Constraints which indicates that while the Absolute Orient and GS constraints are satisified individually, there are no GS at the V3PA we specified. Note that the on the GROUP and SAME ORIENT constraints just indicate that since at least one of the Visits is unschedulable, the ensemble is unschedulable.

To see this visually, we can bring up Aladin. Bring up a DSS image, turn on the FOV, and load JWST GS (guide stars). We can see that there are no Guide Stars in the FGS's for the first observation. You could try and rotate the apertures to find a position angle where there are Guide Stars in the FGSs for both observations, but there is a report in the VP that makes this more straightforward

To see which V3PA values have Guide Stars, we first must remove the V3PA requirement and rerun the Observation through the Visit Planner. Now we can bring up the Display Guide Star Availability report which shows the number of visits with Guide Stars for each V3PA value; note that the report is just providing Guide Star information, so shows all V3PA values, not just those that are actually available. The report can be accessed by right clicking on the Observation name. Hovering the cursor on a portion of the graph shows which visits have no Guide Stars.

We see that V3PA of 183 has only 1 of the visits schedulable, So, we need to revise our V3PA to be 185.

Last modified: November 24, 2017.